Thyroid malignant peripheral nerve sheath tumors(TMPNST) are very rare neoplasms that can be confused with anaplastic carcinoma, Riedel’s thyroiditis,or other soft tissue tumors that may occur in the thyroid region.An example of TMPNST is presented in this report. The tumor occurred in a 64-yrs-old woman.Fine needle aspiration did not provide enouph material.The diagnosis of TMPNST was established by a combination of microscopic,immunohistochemical,and molecular and electron microscopic studies.Tumor cells were focally positive for keratins,a feature that has not been described in peripheral nerve sheath tumors of the thyroid,but that has been occasionally seen in tumors from other locations.A diagnosis of Thyroid cancer cT4NxMx,Total thyroidectomy with frozen section,SND surgery was planned and Thyroidectomy left/R-2/ surgery was performed because the tumor had infiltrate the trachea.After surgery,radiotherapy was offered, but the patient refused this treatment.Unfortunately, the patient died 3 months after surgery. MPNSTs of the thyroid gland very uncommon,with fewer than 30 cases reported in the medical literature to date. As of February 2023,it was registered for the first time in the Department of Head and Neck Surgery of the National Cancer Center of Mongolia.